Rotary pump



ROTARY PUMP Filed Apri1 8,- 1957 4 Sheets-Sheet 1 INVENTOR. ROBERT J.BROWNE BY f ATTOR EY March 20, 1962 R. J. BROWNE 3,025,802

ROTARY PUMP Filed April 8, 1957 4 Sheets-Sheet 2 Fig. 4

lNVENTOfi.

ROBERT J. BROWNE Fig. 5 BY March 20, 1962 Filed April 8, 1957 R. J.BROWNE ROTARY PUMP 4 Sheets-Sheet 5 INVENTOR. ROBERT J. BROWN E BY 4/$52M; Y

March 20, 1962 R. J. BROWNE 3,025,802

ROTARY PUMP Filed April 8, 1957 4 Sheets-Sheet 4 IN V EN TOR. ROBERT J.BROWNE ATTORNEY 3,025,302 ROTARY PUMP Robert J. Browne, St. ClairShores, Mich, assignor to Eaton Manufacturing Company, Cleveland, Ohio,a corporation of Ohio Filed Apr. 8, 1957, Ser. No. 651,545 27 Claims.(Cl. 103-135) This invention relates to a rotary pump of the typewherein a plurality of pumping elements are drivingly disposed in arotor member contained within a housing provided with a cam meansencompassing the rotor, and which provides a sealing surface and aworking surface for the pumping elements. Rotary pumps of this typeheretofore known have not operated satisfactorily at pres sures inexcess of 200 or 300 psi. In automotive applications of pumps of thistype, it is necessary to provide a pumping means which possessessatisfactory flow characteristics over a much higher pressure range anda wide speed operating range.

The structure described herein is illustrated as a roller pump having aplurality of rollers disposed in notches or slots in the rotor in amanner such that the rollers are free to move circumferentially anappreciable amount with respect to the rotor when the rollers are in aradially outward position and are substantially confined when therollers are disposed radially inward. It is to be noted, however, thatsome of the novel features of the structure disclosed herein can beutilized with a pumping structure having other type pumping elements,such as substantially rectangular shaped slippers, vanes, etc., the onlyrequirement being that the pumping elements be moved with respect to therotor. A cam means is disposed in encompassing relation to the rotor andpumping elements and is provided with a constant radius portion whichextends across the arcuate surface between the end of the discharge portand the beginning of the intake port to provide a sealing surface orarc, and a further constant radius portion of a greater radius whichextends substantially across the arcuate portion between the end of theintake port and the beginning portion of the discharge port to provide apumping surface or arc. The developed cam surface extending from thebeginning of the intake port substantially to the end of the intake porthas an intermediate portion of greater radius than the radius of theconstant arc portion substantially between the end of the intake portand the beginning of the discharge port so that when the charge of oiltrapped between adjacent pumping elements is traversed through theintake arc, there is an ove-rfilling before that volume is communicatedto the pumping arc. This feature is to insure that the pump will fillcompletely, thus eliminating cavitation and noise. Also, thisarrangement results in a slight precompression of the entrapped fluidwhich collapses any air bubbles present in the fluid.

Another novel aspect of this pump is the arrangement of the dischargeport with respect to the pumping arc. The arcuate length of the pumpingarc is equal to the arcuate distance measured on the cam are betweenadjacent pumping elements. When the leading pumping element commences tomove inwardly on the cam surface, the entrapped volume between theleading and trailing pumping elements is decreased, resulting in afurther increase in pressure of the oil which is entrapped between theadjacent pumping elements. The ports are arranged for optimum conditionsfor the most frequently used operating condition. However, there will bea tendency to overcompress this entrapped volume at other speeds andviscosities. At this time, the leading pumping element will be movedaway from the trailing portion of the rotor slot as soon as pressure inexcess of that in the discharge port is created, thereby providingadditional communi- 3,025,802 Patented Mar. 20, 1962 cation between theentrapped volume and the discharge means. This check-valve action limitsthe pressure buildup in the entrapped volume to a pressure slightly inexcess of the pressure existing in the discharge means.

An object of this invention is to provide a fluid pumping means whichhas optimum operational features at both low and high speed and high andlow fluid pressure throughout the viscosity range of the fluid.

Another object is to provide means to insure complete filling of thepump.

A further object is to provide pumping elements that move outwardly onthe inlet stroke Without the use of springs or exposure of the pumpingelement to discharge pressure.

A still further object is to provide a pump structure wherein a rotortype seal or a pumping element type seal can be utilized without anystructure modifications in the pump.

Another object is to provide means to eliminate mechanical and fluidnoises in the pump.

These and other objects and advantages will become more apparent fromthe following detailed description of the device and from theaccompanying drawings wherein:

FIGURE 1 illustrates the external pump housing viewed from the coverside of the pump.

FIGURE 2 is a section taken on 2-2 of FIGURE 1.

FIGURE 3 is an internal end view of the pump body taken on 33 of FIGURE2 but with the pump rotor removed.

FIGURE 4 is a section of the pump body.

FIGURE 5 illustrates the internal side of the pump cover.

FIGURE 6 is a section of the pump cover.

FIGURE 7 is a schematic showing of superimposed portions of the pumpwith a portion of the rotor rotated to two different positions.

FIGURE 8 is a view of the rotor and body with the cover removed, and

FIGURE 9 is a partial view of a modification of FIG- URE 8.

Referring to the drawing for a more detailed description of the device,a pump 10 is provided with a body portion 12 and a cover portion 14disposed adjacent thereto. The body and cover are adapted to be held inassembled relation by a plurality of bolts or studs 15 and locating pins16. A rotor shaft having end portions 18 and 20 is supported in the bodyand cover portions by' means of sleeve hearings or bushings 22 and 24,respectively. An intermediate portion of the rotor shaft has keyedthereto a rotor 26 so that rotation of the rotor shaft results inrotation of the pump rotor. A cam ring 27 having a cam surface orperipheral wall 27 is receivable within the working chamber provided inthe body 12 and is fixed from rotation with respect to the body portionby a suitable pin means. It is to be understood that the cam surface canbe formed as an integral part of the pump body and is illustrated as aseparate ring meansfor ease of manufacture.

The body portion 12 is provided with a fluid inlet conduit 28 which iscommunicable through a passage 48 with the intake ports 30 and 32arranged in an end wall of the working chamber. Discharge ports 34 and36 are also provided in the working chamber end wall and are comprisedof arcuate recesses in the end wall of the pump body pumping chamber andare disposed opposite to discharge ports formed in the cover member, tobe hereinafter described. Cam ring 27 is provided with an arcuatelyextending cutout portion 37 which extends circumferentially a shortdistance past the end of discharge port 54;. An opening 38 is providedin the sealing face of body portion 12 and communicates with an opening49 formed in the sealing face of cover 14. A bore 41 is also provided inthe cover 14 which is adapted to receive a flow control valve mechanism.The details of the flow control valve mechanism form no part of thepresent invention and it is of a structure similar to that disclosed inUS. Patent a t-2,752,853, patented July 3, 1956. A passage 42 is incommunication with opening 40, bore 41 and a smaller passage 43 whichcommunicates with intake port 32'.

The cover member 14 also has provided therein intake ports 30 and 32'and discharge ports 34 and 36. When the body portion and cover portionare assembled, ports 30, 32, 34, and 36 are disposed oppositely to ports30, 32', 34', and 36, respectively. Also disposed in the cover portionas shown in FIGURE 5, is a communicating portion 44 which provides forflow of fluid from the discharge ports 34' and 36 to the flow controlvalve disposed in bore 41, and thence to a discharge conduit 46 which isalso formed in the cover member.

The communicating passage 48 is provided in the body member to providefor flow of fluid from intake conduit 23 and opening 38 to intake ports39 and 32. When the flow requirements are such that only a portion ofthe discharge is required, the flow control valve (not shown) functionsto bypass the remainder of the discharge through passage 42 to passage43 and inlet port 32 and through opening 40 in the cover and opening 38in the body, back to communicating means 48 which is in communicationwith the inlet ports Stl and 32. It is to be noted however, that thenovel aspects of this pumping mechanism, to be hereinafter described,can be utilized without a flow control or pressure relief valve means,and such flow control valve means is shown merely to illustrate thenovel pump device in an exemplary structure.

FIGURE 7 is a composite view showing rotor 26, cam surface 27, and theintake and discharge ports which are formed in the body member. Thisview is merely a schematic representation of the novel structure and isnot intended to be an actual representation along any given section. Fordescriptive purposes, a portion of rotor 26 is shown at one positionspanning arc DE and in another position spanning arc AB. FIGURE 8 showsthe complete rotor and for purposes of description, reference Will behad to FIGURES 7 and 8 in the following explanation of the pump.Referring to FIGURE 7, cam surface 27' is provided with aninner-peripheral surface 66 which is comprised of a constant arc portionAB having a radius R which is referred to as a seal arc.

Arcuate portion B-C is a developed cam surface having a radius R at thepoint B with the radius becoming progressively larger as the cam surfaceapproaches point C until it reaches the maximum radius R at point C.Arcuate portion CD is also a developed cam surface with the maximumradius R at the point C progressing to a minimum radius R, at point D.The arcuate portion BD is designated as the intake arc. A pumping areportion DE has a constant radius R and a discharge are portion EA has amaximum radius R at point E, diminishing progressively to a minimumradius R at point A. A plurality of equally spaced slotted portions 68are provided in rotor 26. Each of the slots is comprised of a trailingwall portion 72 and a leading wall portion 74 which are disposed in amanner such that when pumping element 70 is in the radially innerposition, the pumping element is substantially confined, but whenelement 70 is in a radially outer position, it is free to movecircumferentially with respect to the rotor along the walls of the camsurface. By using a rotor element with divergent slot walls, it ispossible to design a slot that can be machined by hobbing or similargenerated cutting means which is more economical than machining parallelsided slots. Although the divergent slot design is preferable for thisand other reasons to be hereinafter discussed, many of the novelfeatures disclosed hereinafter would also apply to devices usingparallel sided slots.

For a pump having a 2.00" diameter rotor, the total clearance betweenthe pumping element and the slot walls when the pumping element is incontact with the cam surface at the radius R is on the order of Thisclearance would vary for an increased or decreased rotor diameter.

Also, by disposing the slot walls at an outwardly divergent angle, thewail clearance between the slot and the pumping element is graduallyincreased as the pumping element progresses along the cam rise on theintake arcuate portion which allows the fluid to be moved outwardly bycentrifugal force to the radially outer portion of the volume to befilled, thus aiding in the filling of that volume. This filling actionoccurring from the root of the slot also provides a force to augmentcentrifugal force to move the pumping element outwardly on the intakestroke. The bottom portion 76 of the slot is shaped in a manner toinsure adequate filling of the bottom portions when the rotor slots arecommunicated with the intake port 32 at the beginning of the intakecycle. On the example cited here using /2 diameter rolls, it isnecessary to have approximately clearance at the root in a slot having asubstantially flat wall bottom portion or an equivalent clearance volumewhen other bottom shapes are used.

Pushing elements 70 are shown as being circular in cross-section andhaving a hollow interior portion. Hollow pumping elements are utilizedto reduce the mass of the elements so that the elements respond morereadily to the forces acting on them as will be hereinafter disclosed.

A seal groove 78 is formed in cam ring 27 so that the base portion 80 ofthe groove communicates with an arcuately extending cutout portion 79formed in the cam ring and tapers to an apex 82 spaced from cutoutportion 79.

A tapering opening is formed at the end of port 32 in body member 12 andis designated as an intake groove 84 which has a base portion 86 incommunication with the end of intake port 32 and an apex portion 88spaced therefrom.

A discharge groove 90 is also formed in body member 12 and has a baseportion 92 in communication with the beginning of discharge port 36 andan apex portion 94 spaced therefrom. The apex portions 88 and 94 of theintake groove and the discharge groove, respectively, arecircumferentially spaced in a manner such that a rotor slot 68 ispositionable so that when the trailing edge 72 of the slot 68 iscoincident with apex 88 of intake groove 84, the leading edge 74 of slot68 is coincident with apex 94 of discharge groove 99. This relationshipcan be varied, depending on the operating pressure range of the pump;for example, at extremely high pressure, the apex 94 of discharge groove90 should be slightly advanced in the direction of rotation and due tothe amount of bleed-back of high pressure fluid, the effectivepositioning of the beginning of the discharge groove would then be at aposition similar to that shown in FIGURE 7 when the pump is operating ina lower pressure range. It is to be noted that the intake and dischargegrooves are radially positioned at a point to communicate with thebottom of the rotor slots because this portion of the slots is mostdifficult to fill.

A discharge extension portion 96 is also formed in the body member andhas an end portion 97 in communication with the end of discharge port 36and the closing end portion 98 spaced therefrom. This groove is notrestricted to the shape shown in the drawing. It is to be noted thatgrooves 84 and 90, and discharge extension portion 96 could be providedin the pump cover instead of the body, or both, with a necessarydecrease in size if provided in both locations, and are shown in thebody merely for manufacturing convenience. Also, seal groove 73 could beformed in the body or cover, or both, insteadof cam. ring 27.

Before setting forth the specific operating details and cooperativerelationship of the cam surface, rotor slot shape, and positioning ofthe ports with respect to the various portions of the cam surface, abrief operating cycle Will be set forth. Fluid flows from a reservoir(not shown) and/ or the discharge side of a fluid operated circuit (notshown) through fluid inlet conduit 28, passage 48 and into intake ports30, 32, 30-,and 32'. Pump rotor 26 is driven from a suitable source andpropels the fluid through the pumping cycle and into discharge ports 34,36, 34- and 36' under pressure. The pressurized fluid flows from thedischarge ports through communicating portion 44 into a flow controlvalve (not shown) which is adapted to be positioned in bore 41. Acharacteristic of the flow control valve is that only a predeterminedmaximum quantity of fluid per unit of time is allowed to pass throughthe valve and into discharge conduit 46. The remaining quantity of fluidis bypassed by the valve so that the remaining quantity flows throughopening 40 and back to the inlet side through a first path 42, 43 and asecond path 38, 48. As heretofore noted, the flow control valvestructure is disclosed in detail in US. Patent No. 2,752,853.

In a rotary pump having pumping elements in contact with an encompassingcam surface, a major problem is that of sealing between the end of thedischarge port and the beginning of the intake port. If a structure isutilized wherein the seal is obtained by maintaining a very close fitbetween the rotor and cam surface in the arcuate portion between the endof the discharge port and the beginning of the intake port, desirablepump operation can be obtained, but the problem of maintaining thenecessary tolerances between the rotor and cam means are veryobjectionable.

If a structure is utilized wherein the seal between the end of thedischarge port and the beginning of the intake port is obtained bymaintaining a seal between the pumping element and cam surface, andbetween the pumping element and rotor slot, the clearance problembetween the rotor and cam surface is eliminated but other objectionableproblems are encountered. These problems are created by the fact thatthe pumping element must seal against the leading wall of the slotinstead of the trailing wall where it normally rides. This movement ofthe pumping element in the slot can create objectionable mechanicalnoise.

The instant pump is of novel design such that regardless of whether arotor type seal is utilized, that is, close clearance between theperiphery of the rotor and the inner-periphery of the cam means acrossthe arcuate surface between the end of the discharge port and thebegining of the intake port, or a pumping element type seal is utilized,the pump will operate with maximum efficiency at either low or highspeed operating conditions and possesses the same flow characteristicsindependent of the type of seal which is utilized Without anyobjectionable mechanical noise.

The structure and operation of the pump will now be discussed wherein apumping element type seal is utilized as illustrated in FIGURE 9. Theinner-peripheral arcuate portion of cam 27 is a constant radius portionwith a clearance on the order of .005.025" between the periphery ofrotor 26 and the cam surface AB as shown at 29 in FIGURE 9. Cam portionB-C has a radius R at point B and increases in radius progressively to aradius R at point C. Assuming that a given pumping element is at thepoint B, the rotor 26 carries the pumping element counterclockwisethrough the arc B-C with the pumping element moving progressivelyoutward in contact with the increasing radius of the cam surface.Obviously, as this pumping element is being swept through the arc B-C,all of the other pumping elements are being moved in a counterclockwisedirection along with the rotor member, and a volume of fluid is disposedbetween adjacent pumping elements as they pass through the intake cycle.

6 It is important to note that while centrifugal-force is perhaps theprincipal force that starts the pumping element IIlOVll'lg outwardly asit leaves the radius R there are also other forces involved in keepingthe pumping element firmly against the cam surface. First, it isdesirable to open the inner inlet port 32 before the outer inlet port30. The resulting flow creates a slight pressure differential across thepumping element that augments centrifugal force. Secondly, the root ofthe slot must be formed as previously mentioned to admit oil between thepumping element and the inner diameter of the slot. Thirdly, the portsare proportioned so a stubstantial amount of oil must flow from theinner inlet port past the pumping element to help fill the increasingvolume disposed between adjacent elements. This flow of oil also createsa pressure differential to aid in maintaining the pumping element inposition. The rotor design using divergent sided slots is valuableherein assisting the pumping element to move outwardly by givingsubstantial freedom to the pumping element and also in permittingsubstantial amount of oil flow around the element.

The volume of fluid entrapped between adjacent elements is progressivelyincreased as the rollers move from the point B to the point C. Thearcuate cam surface CD has a radius R at the point C which is greaterthan the radius R at the point D. Therefore, the leading roller is movedinwardly from the point C to the point D, a distance equal to thedifference between R and R It is to be noted that when the contact point.between the leading pumping element and thecam surface is coincidentwith a radius line drawn through point D, the trailing wall portion 72'of the rotor slot'is coincident with the apex 88 of intake groove 84,and therefore, at this point, the rotor slot which carries the leadingpumping element, passes out of communication with the intake groove.

Obviously then, while the trailing pumping element is being swept fromthe point C to point D, the rotor slot which carries the pumping elementis still in communication with the intake port and also, it is to benoted that the trailing pumping element is moved radially inward due tothe difference in radius R and R There is therefore, an over-fillingeffect becausethe radius of the cam surface at an intermediate point(point C) is greater than at the end of the intake cycle (point D). Thisstructure insures that there will be an adequate filling of the volumebetween the leading and trailing pumping elements. Total filling ofcourse, is of utmost importance because if the entrapped volume to beswept into the pumping are is not completely filled, back-filling cantake place when this volume of oil is communicated with the dischargeport and also, the physical capacity of the pump is not completelyutilized, which results in a decreased output of the pump and irregularand intermittent flow characteristics. When the trailing pumping elementis being swept from point C to point D, the excess amount of entrappedfluid is pumped through intake groove 84 and into the successivetrailing volume of oil wherein the aforementioned trailing pumpingelement is the leading element. At this point, therefore, due to theoverfilling function which is brought about the maximum radius of thecam surface being intermediate the beginning and the end of the intakeports in cooperation with the intake groove which allows excess fluid tobe pumped into the next trailingvolume through intake groove 84, thevolume defined by the leading pumping element and the trailing pumpingelement is completely filled with oil and the trailing pumping elementis now at a point ready to enter the pumping arc which is defined by thearcuate portion of the cam surface between points D and E. While thetrailing pumping element is being traversed through the arc C-.D,communication 'between the entrapped volume and intake port 32 isgradually reduced due to the configuration of intake groove 84 and thetrailing pumping element continues to move radially inward due to theshape of the cam surface, thus increasing the fluid pressure in theentrapped volume before communication with discharge groove 90 iscommenced. This arrangement insures a precompression of the entrappedvolume sufliciently to collapse any air bubbles which might be presentin the fluid. If air bubbles are present in the entrapped volume whencommunication with the discharge means is commenced, a condition similarto cavitation is caused by the shock and noise which occurs when the airbubbles are collapsed in the discharge means.

It is to be noted also that the pumping elements are in an abuttingrelation with the trailing wall portion 72 of each slot at all timeswhile the pumping elements are swept through the arcuate portion definedbetween points B and D due to the tendency of the pumping elements tolag relative to the rotor and also because the frontal or leadingportion of each of the pumping elements is always under a fluid pressureequal to or greater than the fluid pressure imposed on the trailing orrear surface of the pumping element after the pumping element is in acounterclockwise position slightly past point B.

The arcuate portion of the cam surface between points D and E is aconstant radius portion having a radius R The included angle betweenpoints D and E is substantially equal to the angular distance betweencorresponding portions of adjacent rotor slots. Assuming that thetrailing roller is still at the point D and there is a full volume ofoil entrapped between the leading and trailing pumping elements, thepumping elements are moved counterclockwise by the rotor 26 and sincearcuate cam surface DE is a constant radius portion, the trailingpumping element does not move radially as it passes from point D topoint B, but the leading pumping element moves radially inward alongarcuate portion EA. The movement of the trailing pumping element fromthe point D to point E represents the pumping arc of the pump. Duringthis movement of the trailing pumping element from the point D to thepoint E, there is a peculiar cooperation between the discharge grooveand the ability of the leading pumping element to advancecircumferentially with respect to the rotor. As soon as the trailingpumping element progresses an increment past point D, the apex portion94 of discharge groove 90 is communicable with the volume of fluidentrapped between the leading and trailing pumping elements. Due to theconfiguration of the discharge groove, this opening becomesprogressively larger as the rotor moves ahead. At the same time, due tothe decrease in radius of the arcuate portion EA, the leading pumpingelement moves radially inward, thereby decreasing the entrapped volumeand tending to increase the pressure of the fluid confined therein.Since the flow of fluid through the discharge groove 90 into thedischarge port 36 and discharge conduit is less than the amount of fluidactually pumped due to the advance of the rotor and there is, therefore,an increase in pressure in the entrapped volume to a value above thepressure in the discharge port. The frontal or leading portion of theleading pumping element and the bottom or radially inward portion of theleading pumping element is exposed to discharge pressure and thetrailing radially outer quadrant of the leading pumping element isexposed to the pressure of fluid in the entrapped volume. When thepressure differential reaches a given magnitude, the increased pressureexerted on the trailing radially outer quadrant of the leading pumpingelement becomes sufficiently high to cause the leading pumping elementto advance with respect to rotor 26, thereby breaking the seal betweenthe leading pumping element and the trailing wall portion 72 of theleading pumping element slot. Obviously, the pressure in the entrappedvolume will only momentarily be higher than the pressure in thedischarge means and only reaches a magnitude suflicient to advance theleading pumping element with respect to the rotor enough to allowcommunication between the entrapped volume and discharge ports throughthe opening between the leading pumping element and the trailing wallportion of the leading pumping element slot. This pressure differentialis minimized because the portion of the discharge groove incommunication with the entrapped volume is gradually increased whichprovides an increased flow rate through the discharge groove. As therotor continues to advance in a counterclockwise direction, the pumpingaction across the arcuate portion D--E continues and the leading pumpingelement will maintain an advanced position with respect to the rotorsince the opening through the discharge groove is not suflicient toaccommodate all of the pumped fluid.

This phenomena will be hereinafter referred to as the check-valveprinciple. When the increased cross-sectional area of the dischargegroove is sufiicient to carry all of the pumped fluid, theaforementioned unbalanced pressure condition on the leading pumpingelement is overcome, but the leading pumping element remains in aposition adjacent the leading wall of the pumping element slot due to anovel conditon which will be hereinafter discussed in conjunction withdischarge extension 96. This unbalanced pressure condition must, ofnecessity, be overcome after the portion of the leading pumping elementin contact with cam surface 27' communicates with discharge port 34 andthe trailing pumping element slot communicates with discharge port 36.This structure eliminates the difficulty which has heretofore beenpresent in rotary pumps wherein the entrapped volume of fluid wascommunicated to the discharge port before the fluid was raised todischarge pressure, which resulted in a back-flow of fluid from thedischarge conduit into the pumping volume causing fluid shock and veryobjectionable fluid noise along with a very erratic pump output and alsothe condition wherein the entrapped volume of fluid was not communicatedwith the discharge port until the pressure of the entrapped volume ofoil was raised to a pressure considerably higher than the dischargeconduit pressure.

When the trailing pumping element reaches the point B, the pumpingfunction of the leading and trailing pumping elements has been completedand the cycle is repeated with the trailing pumping element thenbecoming the leading pumping element for the next consecutive entrappedvolume of fluid.

When the pumping element which has heretofore been referred to as theleading pumping element reaches the point A, it is moved radially inwardto a position in which the pumping element is substantially confined inthe rotor. This clearance between the pumping element and the leadingand trailing wall portions is not critical; in a pump having a 2"diameter rotor, the clearance is on the order of .010" which permitseasy manufacturing. However, this circumferential clearance conditioncould cause mechanical noise problems on the transfer from discharge tointake except that the novel discharge extension groove and transitiongroove prevents such noise and will be hereinafter discussed.

When a pumping element is progressing along arcuate portion EA, itadvances circumferentially with respect to the rotor to a positionadjacent the leading wall of the pumping element slot due to theoperation of the check-valve principle and is maintained in an advancedposition in the following manner. The beginning of discharge port 37 isadvanced in the direction of rotation with respect to point A in amanner such that the leading pumping element has traversed anappreciable portion of the discharge are before communicating with theouter discharge port, and as the leading pumping element continues to beswept through the discharge arc, flow into the discharge port 37 isrestricted due to the size of the opening with respect to the amount offluid to be pumped. Such restriction results in an increase in pressureon the trailing portion of the pumping element which maintains thepumping element in a position adjacent the leading wall of the pumpingelement slot. This pressure condition continues throughout most of thedischarge cycle which insures that the pumping element will maintain anadvanced position with respect to the pumping element slot until thepumping element approaches the point A.

When the pumping element advances toward the leading wall of the rotorslot, immediate contact is prevented due to a retarding effect caused bythe fluid buildup in front of the pumping element, the fluid buildup onthe leading wall of the slot caused by the rotation of the pumpingelement in the slot, and the fluid buildup or stagnant layer on the camsurface. The force acting to advance the pumping element with respect tothe rotor (due to the advanced position of discharge port 37) is notsuflicient to overcome the aforementioned fluid conditions. The partialadvance of the pumping element up to this point does not result in anyobjectionable mechanical or fluid noise because the aforementioned fluidconditions act to prevent impact of the pumping element against theleading wall of the pumping element slot.

The discharge extension 96 is in communication at end 97 with dischargeport 36 and has a closing end portion 98 remote from discharge port 36.This discharge extension is not restricted to the shape shownin thedrawing, but can be of any shape as long as it is, in effect, anextension of the inner discharge port.

Seal groove 78 which is in communication with the beginning of intakeport 30, is formed at the end of constant arc portion AB and increasesin cross-sectional area in a counterclockwise direction. When thepumping element immediately ahead of the leading pumping element is atthe point B, a continued movement of the rotor brings that pumpingelement into communication with seal groove 76, thereby providingcommunication between intake port 30 through seal groove 78 and theradially outer leading quadrant of the leading pumping element. At thispoint, the radially inner quadrants and trailing radially outer quadrantof the leading pumping element are still in communication with dischargeextension 96. Due to the shape of seal groove 78, communication of thepumping element immediately ahead of the leading pumping element'withintake port 30 is very gradual and consequently, the pressure exerted onthe radially outward leading portion of the leading pumping element isdropped from discharge pressure to intake pressure very gradually. Sincethe trailing portion of the leading pumping elementis still incommunication with discharge extension 96, the differential pressurecondition causes the leading pumping element to gradually penetrate theaforementioned stagnant layers of fluid and move from a positionadjacent to the leading'wall of the rotor slot to a position in contactwith the leading wall. When the leading pumping element comes intocontact with the leading wall of the rotor slot, the sealing function istransferred from the pumping element immediately ahead of the leadingpumping element to the leading pumping element.

This portion of the cycle is repeated when the radially outer trailingquadrant of the leading pumping element communicates with seal groove 78and the trailing pumping element is gradually advanced into contact withthe leading wall of its rotor slot, and the scaling function is at thattime assumed by the trailing pumping element.

It is to be noted that discharge extension 96 also functions to maintainthe pumping elements in contact with the cam surface while the pumpingelements are being swept from the discharge to the intake because byhaving the bottom portion of the pumping elements in communication withthe discharge means until the outer portion of the pumping element iscommunicated with the intake means, the bottom portion of the pumpingelement can never be at a lower pressure than the outer portion.

It is very important to note that the check valve principle, advancedposition of the beginning of outer discharge port '37, the provision ofthe discharge extension 96, and seal groove 78, all cooperate togradually move each of the pumping elements from the trailing Wall tothe leading wall of the rotor slots as the pumping elements are sweptthrough the arcuate portion D-B. This transfer of the pumping elementsfrom the trailing Wall to the leading wall of the rotor slots isnecessary if a pumping element type seal is relied on and with theaforementioned novel means, the advancement of the pumping elements withrespect to the rotor is accomplished without any objectionable noise ina manner heretofore not known or used.

When the leading pumping element reaches a point slightlycounterclockwise past the point B, the filling cycle is again commenced,At this point, therefore, the relationship between the leading pumpingelement and the rotor is restored to a position whereby a seal ismaintained between the pumping element and the trailing wall portionbecause this pumping element has been restored to a state of pressureequilibrium. The pumping element will assume a contact position with thetrailing wall portion of the slot due to the fact that the pumpingelement tends to lag relative to the rotor member and will be maintainedin this position throughoutthe intake cycle due to the fluid forceswhich were considered in a previous discussion of the intake cycle.

Depending upon speed and pressure conditions, when the clearance betweenthe rotor member and the cam ring across the arcuate portion A--B ismaintained at less than approximately .005" for a rotor of approximatelya 2" diameter, a rotor seal is effected across arcuate portion AB. Whensuch a clearance is maintained between the rotor and cam ring, theintake and pumping cycles are identical with the aforementioned pumpingelement seal type pump Where the clerance is more than .005" between therotor member and the cam surface across the arcuate portion AB. With therotor seal, however, there is a pressure gradient across the arcuateportion AB which ranges from discharge pressure at the end of thedischarge port to intake pressure at the beginning of the intake port.Such an arrangement inherently provides for a gradual forward movementof the pumping element with respect to the rotor when the pumpingelement is passing across arcuate portion AB. Therefore, the seal groove78 is not actually needed in a rotor seal type pump, but this sealgroove does not adversely affect the operation of a rotor seal pump inany manner whatsoever. If the clearance is greater than approximately.005", the pump will function as a pumping element seal type pump. Thereis no structure change whatsoever required in the rotor, body, cammeans, or cover to effect this operation. It is noted therefore, thatthis novel structure eliminates the difficulty of maintaining a veryaccurate clearance between the pump rotor member and the cam means.

In summary, a pump structure is set forth in which positive means isprovided to insure complete filling before the pumping cycle is begun.Such means is comprised of the overfilling structure; that is, providinga greater radius at the point C than at the point D, and also providingthe intake and discharge grooves such that if there is too much fluidpresented, the excess fluid is returned to the next preceding volume andthereby provides an additional amount of fluid to fill that volume.Positive means is set forth to insure that the volume pumped across thepumping arc is communicated with the discharge port at the proper timeso that back-filling is eliminated and also, to insure that the pressureof the entrapped volume will not greatly exceed the discharge pressureand thereby cause a fluid shock when the fluid is communicated withdischarge port. In addition, positive means is set forth in the form ofthe discharge extension to prevent leakage between a pumping element andthe arcuate cam surface A-B when the pumping element is passing acrossthis surface. An improved rotor slot design is set forth permittingeconomical manufacture as Well as improved operation. The portingconditions are arranged throughout the operating cycle so as to controlthe movement of the pumping elements to obtain optimum performance withrespect to noise and delivery.

While the present invention has been described in conneotion withcertain specific embodiments, it is to be understood that the foregoingdescription is merely exemplary and that the concept of this inventionis susceptible of numerous other modifications, variations, andapplications which will be apparent to persons skilled in the art. Theinvention is to be limited, therefore, only by the broad scope of theappended claims.

What I claim is:

1. A fluid pumping mechanism comprising a pump housing having a pumpingchamber provided therein, rotor means disposed within said pumpingchamber and rotatable about a fixed center in said housing, intake meansand discharge means communicating with said pumping chamber, saidpumping chamber including a continuous arcuate wall surface, pumpingelements carried by said rotor means for engagement with said arcu atewall surface, a portion of said wall surface having a constant radiusdisposed arcuately between the end of said discharge means and thebeginning of said intake means, another arcuate portion of said wallsurface having a larger constant radius than said radius of said firstmentioned portion and extending substantially between the end of saidintake means and the initial portion of said discharge means, a furtherarcuate portion disposed substantially peripherally coextensive withsaid intake means and having an intermediate arc portion of a radiusgreater than said radius of said second mentioned arcuate portionmeasured from said fixed center, a remaining arcuate portion extendingsubstantially peripherally co extensive with said discharge means havinga radius at an intermediate portion less than the radius of said secondmentioned arcuate portion, and all of said radii being measured from thesame center.

2. A fluid pumping mechanism comprising a housing means having a pumpingchamber therein, intake means and discharge means communicating withsaid pumping chamber, a continuous peripheral Wall means in said pumpingchamber, a rotor rotatably mounted in said chamber, pumping elementscarried by said rotor and constructed and arranged for engaging saidperipheral Wall means, said peripheral Wall means having a first,

arcuate portion of a constant radius and extending between said intakeport and said discharge port, a second arcuate portion having a constantradius greater than the radius of said first mentioned arcuate portionand being disposed substantially diametrically opposed to said firstmentioned arcuate portion, a third arcuate portion disposed in acircumferentially connecting relationship to said first and said secondarcuate portions, an intermediate portion of said third arcuate portionhaving a radius greater than the radius of said second arcuate portionmeasured from the arc center of said second arcuate portion, and a fortharcuate portion disposed substantially opposite to said third arcuateportion and in a circumferentially connecting relationship to said firstand second arcuate portions, an intermediate arc portion of said fourtharcuate portion having a radius less than the radius of said secondarcuate portion, and all of said radii being measured from the samecenter.

3. A fluid pumping mechanism comprising a pump housing having a pumpingchamber therein, intake means and discharge means communicating withsaid pumping chamber, said pump housing being provided with a continuousperipheral wall, a rotor disposed in said chamber, pumping elementscarried by said rotor and constructed and arranged for engaging saidperipheral wall, said peripheral Wall comprising an intake arc portion,a pumping arc portion having a constant radius, a discharge are portionand a seal arc portion, said seal arc portion having a constant radiusless than the constant radius of said pumping arc portion, and saidintake arc portion having an intermediate portion of a radius greaterthan the radius of said pumping arc portion, all of said radii beingmeasured from the same center.

4. A fluid pumping mechanism comprising a pump housing, a pumpingchamber disposed in said pump housing, intake means communicating withsaid pumping chamber, rotor means disposed in said pumping chamber andhaving a plurality of circumferentially spaced slots therein, each ofsaid slots having a radially inner portion and a radially outer portion,said radially outer portion being wider than said radially inwardportion pumping elements of a width substantially less than the radiallyouter portion of said slots and being freely movable circumferentiallyin said radially outer portion of each of said slots, said pumpingchamber having a continuous peripheral wall means including a fluidintake arc surface means in communication with said intake means, saidpumping elements being engageable with said continuous peripheral wallmeans, said fluid intake are surface means having an intermediate arcportion of a greater radius than the radius of any remaining portion ofsaid continuous peripheral wall means measured from the arc center ofsaid intermediate arc portion, discharge means communicating with saidpumping chamber, a fluid entrapping means comprising juxtaposed pumpingelements and portions of said rotor and said continuous peripheral wallmeans lying substantially between said juxtaposed pumping elements, saidcontinuous peripheral Wall means including a fluid discharge are surfacemeans in communication with said discharge means, means including saidfluid discharge are surface means for creating discharge fluid pressurein said discharge means and creating a differential fluid pressure insaid fluid entrapping means with respect to the discharge fluid pressurewhen said fluid entrapping means is traversing said fluid discharge aresurface and is isolated from said intake means and in restrictedcommunication with said discharge means, to move one of said juxtaposedpumping elements to open said fluid entrapping means into communicationwith said discharge means whereby fluid in said fluid entrapping meansis vented to the discharge means before the fluid entrapping means is incircumferential overlapping relationship with the discharge meansallowing freely open communication therebetween.

5. A fluid pumping means comprising a pump housing, a pumping chamberprovided in said housing, a pump rotor disposed in said pumping chamberand being rotatable relative to said housing, a plurality ofcircumferentially spaced slots in said rotor, a plurality of pumpingelements disposed in said slots, said slots having a circumferentiallength along the periphery of said rotor substantially greater than thewidth of said pumping elements, intake means and discharge meanscommunicable with said pumping chamber, said pumping chamber having acontinuous peripheral wall means including a fluid intake arc surfacemeans in communication with said intake means, said pumping elementsbeing engageable with said continuous peripheral wall means, said fluidintake are surface means having an intermediate arc portion of a greaterradius than the radius of any remaining portion of said continuousperipheral wall means measured from the center of rotation of saidrotor, a fluid enclosure means comprising juxtaposed pumping elementsand portions of said rotor and said continuous peripheral Wall meanslying substantially between said juxtaposed pumping elements, saidcontinuous peripheral wall means including a fluid discharge are surfacemeans in communication with said discharge means, means including saidfluid discharge are surface means for creating d ischarge fluid pressurein said discharge means and creating a fluid pressure suflicientlyhigher than discharge pressure in said fluid enclosure means when saidfluid enclosure means is traversing said fluid discharge are surfacemeans and is isolated from said intake means and in restrictedcommunication with said discharge means, to move one of said juxtaposedpumping elements to open said fluid enclosure means into communicationwith said discharge means whereby fluid in said fluid enclosure means isvented to said discharge means before said discharge means is in freelyopen communication with said fluid enclosure means.

6. A fluid pumping mechanism comprising a pump housing having a pumpingchamber provided therein, rotor means disposed within said pumpingchamber, a plurality of circumferentially spaced slots provided in saidrotor means and each of said slots having a leading wall portion and atrailing wall portion, intake means and discharge means communicatingwith said pumping chamber, said pumping chamber having a continuousperipheral wall, a pumping element positioned in each of said slots forengaging said peripheral wall, said peripheral wall comprising an intakearc portion, a pumping arm portion having a constant radius, a dischargearc portion, and a seal arc portion, said seal arc portion having aconstant radius less than the constant radius of said pumping arc andsaid intake arc portion having an intermediate portion of a radiusgreater than the radius of said pumping arc portion, and all of saidradii being measured from the same center.

7. A device according to claim 6, wherein the radius of said rotor meansis substantially less than the radius of said seal arc portion to allowa relatively free flow of fluid between said rotor and seal arc portion.

8. A device according to claim 6, wherein the radius of said rotor meansis substantially equal to the radius of said seal arc portion to form arelatively fluid tight seal between said rotor and said seal arcportion.

9. A device according to claim 6, wherein said intake means comprises anintake groove and an intake port, and said discharge means comprises adischarge groove and a discharge port.

10. A device according to claim 9, wherein said intake groove and saiddischarge groove are comprised of base portions communicable with saidintake port and said discharge port, respectively, and each having apexportions spaced from said base portions.

11. In a fluid pumping mechanism, a pump housing, a pumping chamberhaving a continuous peripheral wall and being disposed in said pumphousing, intake means and discharge means communicating with said pumphousing, rotor means disposed in said pumping chamber having a pluralityof circumferentially-spaced slots there.- in, each of said slots havingwall portions diverging in a radially outward direction, a pumpingelement disposed in each of said slots for engaging said continuousperipheral wall and being of a width substantially less than the outerportion of said slots, said continuous peripheral wall having an intakearc portion, a pumping arc portion, a discharge are portion and a sealarc portion, said pumping arc portion having a constant radius, saidseal arc portion having a constant radius less than the constant radiusof said pumping arc portion, said in take arc portion having anintermediate arc portion of a radius greater than the radius of saidpumping arc portion, and all of said radii being measured from the samecenter.

12. A device according to claim 11, wherein the radius of said rotormeans is substantially less than the constant radius of said seal arcportion to allow a relatively free flow of fluid between said rotor andseal arc portion, and said intake means comprising a seal groovecommunicable with the end of said intake arc portion adjacent said sealarc portion.

13. A fluid-pumping mechanism comprising a pump housing having a pumpingchamber provided therein, said pumping chamber being provided with acontinuous peripheral wall, rotor means disposed within and rotatableabout a fixed center in said pumping chamber, a plurality ofcircumferentially-spaced slots provided in said rotor means and having aradially inner portion and a radially outer portion, said radially outerportion being wider than said radially inner portion, hollow circularpumping ele ments of a diameter substantially less than the radiallyouter portion of said slots and being freely movable circumferentiallyin said radially outer portion of each of said slots for engaging saidperipheral wall, intake means communicable with said pumping chambercomprising a seal groove, an inner intake port, an outer intake port,and an intake groove, discharge means communicable with said pumpingchamber and comprising a discharge groove, an inner discharge port andan outer discharge port, said peripheral wall having an intake arcportion, a pumping arc portion having a constant radius, a discharge areportion and a seal arc portion, said seal arc portion having a constantradius less than the constant radius of said pumping arc and said intakearc portion having an intermediate portion of a radius greater than theradius of said pumping arc portion, and all of said radii being measuredfrom the same center.

14. A device according to claim 13 wherein said seal groove iscommunicable with said radially outer intake port, said intake groove iscommunicable with said radially inner intake port and said dischargegroove and said discharge extension are communicable with said radiallyinner discharge port.

15. A device according to claim 14, wherein the radius of said rotormeans is substantially less than the radius of said seal arc portion toallow a relatively free flow of fluid between said rotor and said sealarc portion.

16. A device according to claim 14 wherein the radius of said rotormeans is substantially equal to the radius of said seal arc portion toform a relatively fluid-tight seal between said rotor and said seal arcportion.

17. A device according to claim 14 wherein the pumping arc portion iscircumferentially arranged with respect to said discharge groove wherebywhen a leading pumping element of a pair of consecutive pumping elementsis traversing the initial portion of said discharge arc, the trailingpumping element is traversing the initial portion of said pumping arcportion and said rotor slot carrying said trailing pumping element hasrestricted communication with said discharge groove so that furthertraverse of said pumping elements results in an increase in fluidpressure of the fluid entrapped between said pumping elements until saidincreased fluid pressure is suflicient to move said leading pumpingelement circumferentially with respect to said rotor to allowcommunication between said entrapped volume and said discharge ports.

18. A fluid pumping mechanism comprising a pump housing, a pumpingchamber disposed in said pump housing, intake means communicating withsaid pumping chamber, rotor means disposed in said pumping chamber andhaving a plurality of radial, outwardly diverging, circurnferentiallyspaced slots therein, a pumping element disposed in each of said slotsand being free to move circumferentially in the radially outer portionof each of said slots, said pumping chamber having a. circumferentiallyextending continuous arcuate surface means including a fluid intake aresurface means in communication with said intake means, said pumpingelements being engageable with said continuous arcuate surface means,said fluid intake arc surface means having an intermediate arc portionof a greater radius than the radius of any remaining portion of saidcontinuous arcuate surface means measured from the arc center of saidintermediate arc portion, discharge means communicating with saidpumping chamber, a fluid enclosure means comprising a pair ofconsecutive pumping elements and portions of said rotor and saidcontinuous peripheral wall means lying substantially between saidconsecutive pumping elements, said continuous arcuate surface meansincluding a fluid pumping arc surface means and a fluid discharge arcsurface means, means including said fluid discharge are surface meansfor creating discharge fluid pressure in said discharge means andcreating a fluid pressure higher than discharge pressure in said fluidenclosure means when the leading pumping element of said pair ofconsecutive pumping elements is traversing the initial portion of saidfluid discharge are surface means and the trailing pumping element ofsaid pair of pumping elements is traversing the initial portion of saidfluid pumping arc surface means and said fluid enclosure means hasrestricted communication with said discharge means whereby relativecircumferential movement is effected between said leading pumpingelement and said rotor, thus providing additional communication betweensaid entrapped fluid and said discharge means.

19. A fluid pumping means comprising a pump housing, a pumping chamberdisposed in said pump housing, a rotor means disposed in said pumpingchamber, a plurality of pumping elements carried by said rotor means andbeing circumferentially movable with respect to said rotor means, saidpumping chamber having a continuous peripheral wall means having anintake arc portion, a pumping arc portion and a discharge arc portion,said pumping elements being engageable with said continuous peripheralwall means, said intake arc portion including an intermediate arcportion having a radius greater than the radius of any remaining portionof said continuous peripheral wall means measured from the arc center ofsaid intermediate arc portion, discharge means communicating with saidpumping chamber and advanced of the pumping arc in the direction of thedischarge are so that a volume of fluid entrapped by a pair ofconsecutive pumping elements which are traversing the pumping arc andthe discharge are respectively, has restricted communication with saiddischarge means when the trailing pumping element of said pair ofpumping elements is traversing the initial portion of said pumping arc,resulting in an increase in fluid pressure of said entrapped volume andcircumferential movement of the leading pumping element of said pair ofpumping elements with respect to said rotor means to allow furthercommunication between said entrapped volume and said discharge means.

20. A fluid pumping mechanism comprising a pump housing having a pumpingchamber provided therein, rotor means disposed in said pumping chamber,a plurality of circumferentially spaced slots in said rotor and eachslot having a leading wall portion and a trailing wall portion, pumpingelements disposed in said slots and being freely circumferentiallymovable with respect to said rotor means, said pumping chamber beingprovided with a continuous peripheral wall means having an intake arcportion, a pumping arc portion, a discharge are portion and a seal areportion, said seal arc portion having a radius substantially greaterthan the maximum radial dimension of said rotor means to allow arelatively free flow of fluid between said rotor means and said seal arcportion, said pumping elements being disposed for engagement with saidcontinuous peripheral wall means, intake means communicable with saidpumping chamber and including a seal groove disposed substantially atthe beginning of said intake arc portion in communication with saidintake means, discharge means comprising a radially inner discharge portand a radially outer discharge port communicable with said pumpingchamber,

'a fluid enclosure means comprising juxtaposed leading and trailingpumping elements and portions of said rotor means and said continuousperipheral wall means disposed substantially between said juxtaposedpumping elements, said trailing pumping element being exposed to fluidpressure in said discharge ports in a direction tending to advance saidtrailing pumping element with respect to said rotor means while saidleading pumping element of said fluid enclosure means is communicablewith said seal groove so that the fluid pressure in said fluid enclosuremeans is gradually diminished to intake pressure, resulting in a gradualforward circumferential movement of the trailing pumping element of saidpair of pumping elements into contact with the leading wall portion ofsaid rotor slot in which said trailing pumping element is positioned.

21. A fluid pumping mechanism comprising a pump housing having a pumpingchamber therein, rotor means disposed within said pumping chamber,intake means comprising a radially inner intake port and a radiallyouter intake port communicating with said pumping chamber, dischargemeans comprising a radially inner discharge port and a radially outerdischarge port communicating with said pumping chamber and wherein saidpumping chamber is comprised of a continuous peripheral wall means,pumping elements carried by said rotor and being movablecircumferentially with respect to said rotor, said pumping elementsbeing engageable with said continuous peripheral wall means, an intakearcuate portion of said continuous peripheral Wall means having anintermediate arc portion of a radius greater than the radius of anyremaining portion of said continuous peripheral wall means measured fromthe arc center of said intermediate arc portion, said continuousperipheral wall means also including a pumping arcuate portion, adischarge arcuate portion and the beginning of said radially outerdischarge port being advanced substantially ahead of said pumpingarcuate portion in the direction of said discharge arcuate portion sothat fluid pumping commences before there is unrestricted communicationbetween the fluid being pumped and said discharge ports.

22. A fluid pumping means comprising a pump housing having a pumpingchamber therein, rotor means disposed within said pumping chamber, anintake port and discharge port communicating with said pumping chamber,said pumping chamber having a continuous peripheral wall means includingan intake arc portion, a pumping arc portion, a discharge are portion,and a seal arc portion, pumping elements carried by said rotor forengagement with said continuous peripheral wall means, said intake arcportion including an intermediate arc portion having a radius greaterthan the radius of any remaining portion of said continuous peripheralwall means measured from the arc center of said intermediate arcportion, and the beginning of said discharge port beingcircumferentially spaced with respect to said discharge are portion sothat fluid pumping commences before there is unrestricted communicationbetween the fluid being pumped and said discharge port.

23. A fluid pumping mechanism comprising a pump housing having a pumpingchamber therein, said pumping chamber having a continuous peripheralwall, intake means and discharge means communicating with said pumpingchamber, said peripheral wall having an intake arc portion, a pumpingarc portion having a constant radius, a discharge are portion, and aseal arc portion, said intake arc portion having an intermediate portionof a radius greater than the radius of any remaining portion of saidperipheral wall measured from the arc center of said intermediateportion of said intake arc portion, rotor means disposed within saidpumping chamber and having a plurality of circumferentially spaced slotstherein, a pumping element disposed in each of said slots for engagementwith said peripheral wall, an intake groove disposed at the end of saidintake means communicable with said intake means in a manner such thatwhen the leading pumping element of a pair of adjacent pumping elementsis approaching the end of the pumping arc, the fluid entrappedtherebetween gradually passes out of communication with said intakemeans so as to slightly precompress said entrapped fluid.

24. A fluid pumping mechanism comprising a pump housing having a pumpingchamber provided therein, rotor means disposed within said pumpingchamber and having a plurality of circumferentially spaced slotsprovided therein, a pumping element provided in each of said slots, saidpump housing being provided with a continuous peripheral wall meanshaving an intake arc portion, a pumping arc portion, a discharge areportion, and a seal arc portion, said seal arc portion having a radiussubstantially greater than the maximum radial dimension of said rotormeans to allow relatively free flow of fluid between said rotor meansand said seal arc portion, intake means including an intake portcommunicable with said pumping chamber, discharge means communicablewith said pumping chamber and comprising a first discharge portcircumferentially partially overlapping said seal arc portion, a seconddischarge port disposed radially outward of said first discharge port, afluid entrapping means comprising successive leading and trailingpumping elements and portions of said rotor means and said continuousperipheral wall means disposed between said successive pumping elements,said trailing pumping element being urged by fluid pressure in saiddischarge ports in an advancing direction with respect to said rotormeans while said leading pumping element of said fluid entrapping meansis communicable With said intake port, means including said intake meansto gradually diminish the fluid pressure in said fluid entrapping meansfrom discharge pressure to intake pressure while said trailing pumpingelement is urged by fluid pressure in said discharge ports in anadvancing direction with respect to said rotor means whereby saidtrailing pumping element is gradually moved forward in its rotor slotinto sealing engagement with a leading wall of said slot to effect aseal so that the trailing pumping element will provide a seal betweenthe discharge means and the intake means.

25. A fluid pumping mechanism comprising a pump housing, a pumpingchamber disposed in said pump housing, intake means and discharge meanscommunicating With said pumping chamber, rotor means disposed in saidpumping chamber, circumferentially spaced openings provided in saidrotor, a pumping element disposed in each of said spaced openings freeto move to a non-sealing position, said pumping chamber being providedwith a continuous peripheral wall surface having an intake arc portion,a pumping arc portion and a discharge are portion, said pumping elementsbeing engageable with said continuous peripheral wall surface, saidintake arc portion having an intermediate arc portion of a radiusgreater than the radius of any remaining portion of said continuousperipheral wall surface measured from the arc center of saidintermediate arc portion, said discharge means being circumferentiallyadvanced of the pumping arc portion in the direction of the dischargeare portion so that when the leading pumping element of a pair ofpumping elements is traversing said discharge are portion, the trailingpumping element of said pair of pumping elements is traversing thepumping arc portion and the pressure of fluid entrapped between saidpair of pumping elements in increased above the pressure of fluiddisposed ahead of the leading pumping element in the discharge meansresulting in relative movement between the leading pumping element andthe rotor, thus providing com- 18 munication between the entrapped fluidand the discharge means.

26. 'In a fluid pumping mechanism, a pump housing having a pumpingchamber therein, intake means and discharge means communicating withsaid pumping chamber, a rotor in said chamber and being rotatable insaid housing, said pumping chamber having a continuous wall surfacemeans including a fluid intake are surface means in communication withsaid intake means, pumping elements carried by said rotor for engagingsaid continuous wall surface means, and said fluid intake are surfacemeans having an intermediate arc portion of a radius greater than theradius of any remaining portion of said continuous wall surface meansmeasured from the arc center of said intermediate arc portion.

27. Apparatus for controlling the inlet of a fluid pump mechanism havinga pumping chamber and a rotor rotatably mounted therein, said pumpingchamber including a circumferentially extending continuous arcuatesurface, pumping elements carried by said rotor for engagement with saidcontinuous arcuate surface, and said continuous arcuate surface havingintake are means, said intake arc means including an intermediate arcportion having a radius greater than the radius of any remaining portionof said continuous arcuate surface measured from the arc center of saidintermediate arc portion.

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FOREIGN PATENTS 19,119 Great Britain 1911 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,025,802 March 20 1962 Robert J.Browne It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent shouldread. as

corrected below.

Column 4, line 26, for "Pushing" read Pumping column 9, llne 37, for"76" read 78 column 1O line 39, for "clerance" read clearance column 11,line 63, for "forth" read fourth (SEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer

